I have run both the Xt and Zees in the Alps and in Scotland. Both are pretty awesome brakes to be honest.
There are some very nit picky comments above that i don’t really agree with. If you are looking for brakes for big descents then obviously the Zees should be your first choice, its what they are designed for. Yep the XT will do, and yep i survived a week in the alps with them and didn’t die but there were more than a few occasions i wanted some more stopping power and modulation and thats exactly what the Zees give me.
They are not particularly heavy, and tbh i am not sure what the lever quality or lack of refers to but they are set up really well for 1 finger braking ( as are the XT to be fair).
My choice would be, for general trail riding and some big days thrown in then XT any day.
For alpine and predominately mountainous terrain then Zee. Hands down.